From bb26c579856ee16cbd5554ac1a37d1cbbfa97d27 Mon Sep 17 00:00:00 2001
From: alexvanin <alexvanin@icloud.com>
Date: Fri, 10 May 2019 12:55:52 +0300
Subject: [PATCH] Added message handling mechanism for discord module

---
 main.go                        |  4 +-
 modules/discord/discord.go     | 26 ++++++++++++-
 modules/discord/handlers.go    | 68 ++++++++++++++++++++++++++++++++++
 modules/discord/testhandler.go | 25 +++++++++++++
 4 files changed, 119 insertions(+), 4 deletions(-)
 create mode 100644 modules/discord/handlers.go
 create mode 100644 modules/discord/testhandler.go

diff --git a/main.go b/main.go
index d2073ab..2196859 100644
--- a/main.go
+++ b/main.go
@@ -34,8 +34,8 @@ func start(p appParam) {
 	if err != nil {
 		log.Fatal("discord: cannot start instance", err)
 	}
-	log.Print("main: discord instance running")
-	log.Print("main: — — —")
+	log.Printf("main: discord instance running")
+	log.Printf("main: — — —")
 
 	<-p.Context.Done()
 	log.Print("main: stopping galched-bot")
diff --git a/modules/discord/discord.go b/modules/discord/discord.go
index c12da33..3a19213 100644
--- a/modules/discord/discord.go
+++ b/modules/discord/discord.go
@@ -2,6 +2,7 @@ package discord
 
 import (
 	"fmt"
+	"log"
 
 	"galched-bot/modules/settings"
 
@@ -11,7 +12,9 @@ import (
 
 type (
 	Discord struct {
-		session *discordgo.Session
+		appVersion string
+		processor  *HandlerProcessor
+		session    *discordgo.Session
 	}
 )
 
@@ -21,10 +24,29 @@ func New(s *settings.Settings) (*Discord, error) {
 	if err != nil {
 		return nil, errors.Wrap(err, "cannot create discord instance")
 	}
-	return &Discord{session: instance}, nil
+
+	processor := NewProcessor(s.Version)
+
+	log.Printf("discord: added %d message handlers", len(processor.handlers))
+	if len(processor.handlers) > 0 {
+		for i := range processor.handlers {
+			log.Printf("discord: %d) %s", i+1, processor.handlers[i].Signature())
+		}
+	}
+
+	return &Discord{
+		appVersion: s.Version,
+		processor:  processor,
+		session:    instance,
+	}, nil
+}
+
+func LogMessage(m *discordgo.MessageCreate) {
+	log.Printf("discord: msg [%s]: %s", m.Author.Username, m.Content)
 }
 
 func (d *Discord) Start() error {
+	d.session.AddHandler(d.processor.Process)
 	return d.session.Open()
 }
 
diff --git a/modules/discord/handlers.go b/modules/discord/handlers.go
new file mode 100644
index 0000000..a7d9234
--- /dev/null
+++ b/modules/discord/handlers.go
@@ -0,0 +1,68 @@
+package discord
+
+import (
+	"fmt"
+	"log"
+	"strings"
+
+	"github.com/bwmarrin/discordgo"
+)
+
+type (
+	MessageHandler interface {
+		Signature() string
+		Description() string
+
+		IsValid(string) bool
+		Handle(s *discordgo.Session, m *discordgo.MessageCreate)
+	}
+
+	HandlerProcessor struct {
+		appVersion string
+		handlers   []MessageHandler
+	}
+)
+
+func NewProcessor(appVersion string) *HandlerProcessor {
+	return &HandlerProcessor{
+		appVersion: appVersion,
+	}
+}
+
+func (h *HandlerProcessor) AddHandler(handler MessageHandler) {
+	h.handlers = append(h.handlers, handler)
+}
+
+func (h *HandlerProcessor) HelpMessage() string {
+	helpMessage := fmt.Sprintf("ГалчедБот версии %s. Описание команд: \n"+
+		"  **!galched** - список команд бота\n", h.appVersion)
+
+	for i := range h.handlers {
+		helpMessage += fmt.Sprintf("  **%s** - %s\n",
+			h.handlers[i].Signature(),
+			h.handlers[i].Description())
+	}
+
+	return strings.TrimRight(helpMessage, "\n")
+}
+
+func (h *HandlerProcessor) Process(s *discordgo.Session, m *discordgo.MessageCreate) {
+	if m.Author.ID == s.State.User.ID {
+		return
+	}
+
+	if strings.HasPrefix(m.Content, "!galched") {
+		LogMessage(m)
+		_, err := s.ChannelMessageSend(m.ChannelID, h.HelpMessage())
+		if err != nil {
+			log.Printf("discord: cannot send message [%s]: %v", h.HelpMessage(), err)
+		}
+	}
+
+	for i := range h.handlers {
+		if h.handlers[i].IsValid(m.Content) {
+			h.handlers[i].Handle(s, m)
+			break
+		}
+	}
+}
diff --git a/modules/discord/testhandler.go b/modules/discord/testhandler.go
new file mode 100644
index 0000000..8ed4370
--- /dev/null
+++ b/modules/discord/testhandler.go
@@ -0,0 +1,25 @@
+package discord
+
+import (
+	"github.com/bwmarrin/discordgo"
+)
+
+type testHandler struct{}
+
+var _ = (testHandler)(nil) // ignore unused warning
+
+func (t *testHandler) Signature() string {
+	return "!test"
+}
+
+func (t *testHandler) Description() string {
+	return "тестовый хэндлер"
+}
+
+func (t *testHandler) IsValid(msg string) bool {
+	return msg == "!test"
+}
+
+func (t *testHandler) Handle(s *discordgo.Session, m *discordgo.MessageCreate) {
+	LogMessage(m)
+}